Question: If $9a + 4b + 5c = -6$ and $6x + 2y + 6z = 9$, what is $40b + 90a + 50c + 60z + 60x + 20y$ ?
Explanation: $= 90a + 40b + 50c + 60x + 20y + 60z$ $= (10) \cdot (9a + 4b + 5c) + (10) \cdot (6x + 2y + 6z)$ $= (10) \cdot (-6) + (10) \cdot (9)$ $= -60 + 90$ $= 30$